<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>03_固定定位</title>
  <style>
  .fu{
    background-color: yellow;
  }
  .fu>div{
    width: 100px;
    height: 100px;
  }
  .z1{
    background-color: red;
  }
  .z2{
    background-color: green;
      /*固定定位：会释放布局空间
      移动参照物：html根元素*/
       position: fixed;
      bottom: 0;
      left: 0;
  }
  .z3{
    background-color: blue;
  }
  </style>
</head>
<body>
<div class="fu">
<div class="z1"></div>
<div class="z2"></div>
<div class="z3"></div>
</div>
</body>
</html>